Color separated films of Y (yellow), M (magenta), C (cyan), and K (black) ink, used in a printing process, wherein black ink is used to control brightness, are typically made by using a color scanner. However, it is difficult to produce a perfect separated color film owing to the lack of manageability of a picture scanner for correcting variations in color and density in the field of color analysis. Furthermore, on occasion it is desired to produce a slightly different color tone from that of the original picture. Such a requirement also goes beyond the capability of prior art devices. In order to compensate for the insufficient functioning of the scanner, correction of color tones is usually done by using a reducer on some parts or on the full surface of the separated color film.
Conventional dot-etching is accomplished by placing a separated color film to be corrected on a retouching bench equipped with a light-table, applying a reducer liquid to the areas to be dot-etched, washing the liquid away with water, and observing the degree and effect of dot-etching on dot size with a magnifying glass. If necessary, the above procedures are repeated until the desired occupation ratio of dots, or dot percentage is obtained. When these procedures are applied to positive films, smaller dots will appear on the resultant print and when applied to negative films, larger dots will appear.
Though color scanners are popular today, the above described dot-etching and other retouching steps are still required thereby. These processes are rather time-consuming and troublesome, even for skilled workers.